1. Field of the Invention
The present invention relates to polymerization catalyst activators, to methods of making these activators, to polymerization catalyst systems containing these activators, and to polymerization processes utilizing the same. More specifically, the present invention relates to a polymerization catalyst activator comprising two or more heterocyclic nitrogen-containing ligands coordinated to a Group 13 atom.
2. Description of the Related Art
Polymerization catalyst compounds are typically combined with an activator (or co-catalyst) to yield compositions having a vacant coordination site that will coordinate, insert, and polymerize olefins. Metallocene polymerization catalysts, for example, are typically activated with aluminoxanes which are generally oligomeric compounds containing —Al(R)—O— subunits, where R is an alkyl group. The most common aluminoxane activator is methylaluminoxane (MAO), produced by the hydrolysis of trimethylaluminum (TMA). MAO, however, is expensive to utilize because it must be added in great excess relative to the metallocene and because of the high cost of TMA. Additionally, MAO tends to be unstable as it precipitates out of solution over time.
As a result, alternative activators for metallocenes and other single-site polymerization catalysts have been discovered in recent years. For example, perfluorophenyl aluminum and borane complexes containing one anionic nitrogen-containing group have recently gained much attention.
Activator complexes having a Group 13 atom have also been suggested as a viable alternative to the expensive aluminoxane activators. For example, U.S. Pat. Nos. 6,147,173 and 6,211,105 disclose a polymerization process and polymerization catalyst where the catalyst includes an activator complex having a Group 13 element and at least one halogenated, nitrogen-containing aromatic group ligand.
Each of these alternatives, including the formation of aluminoxane, require multi-step, complicated syntheses. There is a need, therefore, to provide a simpler method of co-catalyst synthesis and catalyst activation. There is also a need to improve catalyst economics by providing a highly active co-catalyst.